BIOTIC Species Information for Ulva intestinalis
Researched byGeorgina Budd & Paolo Pizzola Data supplied byMarLIN
Refereed byThis information is not refereed.
Reproduction/Life History
Reproductive typeVegetative
Alternation of generations
Developmental mechanismSpores (sexual / asexual)
Reproductive SeasonAll year with summer maximum Reproductive LocationWater column
Reproductive frequencyAnnual protracted Regeneration potential No
Life span<1 year Age at reproductive maturitySee additional information
Generation time<1 year FecundityNot relevant
Egg/propagule sizeNot relevant Fertilization typeExternal
Larval/Juvenile dispersal potential>10km Larval settlement periodNot relevant
Duration of larval stageSee additional information   
Reproduction Preferences Additional InformationSpecies of the genus Ulva are rapidly growing opportunists, favoured by the frequency and speed of their reproduction. The short lived plants reach maturity at a certain stage of development rather than relying on an environmental trigger. Ulva intestinalis can be found in reproductive condition at all times of the year but maximum development and reproduction occur during the summer months especially towards the northern end of the distribution of the species (Burrows, 1991). The life history consists of an isomorphic (indistinguishable except for the type of reproductive bodies produced) alternation between haploid gametophytic and diploid sporophytic generations but can be modified by environmental conditions (Burrows, 1959; Moss & Marsland, 1976; Reed & Russell, 1978). McArthur & Moss (1979) examined the process of gametogenesis and gamete structure using scanning and transmission electron microscopy.
The haploid gametophytes of Ulva produce enormous numbers of biflagellate motile gametes which cluster and fuse to produce a sporophyte (diploid zygote). The sporophyte matures and produces by meiosis large numbers of quadriflagellate zoospores that mature as gametophytes, and the cycle is repeated. Both gametes and spores may be released in such quantities into rock pools or slack water that the water mass is coloured green (Little & Kitching, 1996). Together spores and gametes are termed 'swarmers'. Swarmers are often released in relation to tidal cycles, with the release being triggered by the incoming tide as it wets the thallus. However, the degree of release is usually related to the stage of the spring/neap tidal cycle, so allowing regular periodicity and synchronization of reproduction (Little & Kitching, 1996). Christie & Evans (1962) found that swarmer release of Ulva intestinalis (as Enteromorpha intestinalis) from the Menai Straits, Wales, peaked just before the highest tides of each neap-spring cycle.
Mobility of swarmers belonging to Ulva intestinalis (as Enteromorpha intestinalis) can be maintained for as long as 8 days (Jones & Babb, 1968). Algae such as Ulva intestinalis tend to have large dispersal shadows, with propagules being found far from the nearest adult plants, e.g. 35 km (Amsler & Searles, 1980).
Reproduction References Amsler & Searles, 1980, Knight & Parke, 1931, Little & Kitching, 1996, Burrows, 1959, Jones & Babb, 1968, Moss & Marsland, 1976, Reed & Russel, 1978, McArthur & Moss, 1979,
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